What is Bronchiolitis
Bronchiolitis is an extremely common, acute viral infection involving the bronchioles of the lungs (small air passages). It most commonly occurs in infants and children up to the age of two. "About 25% of infants have bronchiolitis during their first year, and 95% have had the disease by their second birthday" (http://medical-dictionary.thefreedictionary.com). In North America and countries with a moderate climate, incidence usually peaks in winter through late spring. Children in daycare or living in crowded situations and/or exposed to second-hand smoke are most at risk, as are preemies, children born with heart or lung conditions or HIV/AIDS.
The most common cause of bronchiolitis, which affects boys almost twice as much as girls, is RSV (respiratory synctial virus).
Bronchiolitis Obliterans Organizing Pneumonia
Bronchiolitis Obliterans Organizing Pneumonia (BOOP) was first recognized in 1985 and affects adults, as does obliterative bronchiolitis, which I will describe in a minute. While some use the terms obliterans and obliterative interchangeably, this use is incorrect.
BOOP is what happens when scar tissue develops into a polyp inside the bronchioles. It is an inflammatory lung disease with similar features to asthma and COPD, but different enough that treatments for these conditions may not be as effective. Left untreated, however, the small airways will be destroyed. Researchers do not yet know why these polyps form, usually in the new connective tissue that forms in the case of lung transplants.
These types of polyps do occur in other situations, such as most pneumonias, alveolar damage, aspiration, and interstitial pneumonia. But, in the instance of BOOP, the condition is chronic.
Diagnosis is usually confirmed via biopsy, after patient presentation of difficulty breathing, dry cough, fever, crackling, and X-ray presentation of patchy spots in both lungs. "About 50% of cases of bronchiolitis obliterans organizing pneumonia are idiopathic" (http://emedicine.medscape.com)--that is there is no known or discernible cause.
The condition is dense and irreversible, but completely treatable, usually with anti-inflammatories (Prednisone).
Obliterative Bronchiolitis
Obliterative bronchiolitis is a sign of rejection of a lung transplant and happens in about 50 percent of cases. Like BOOP, it is an inflammatory reaction, but in this case white blood cells get into the grafted or transplanted tissue, and as they build up, they end up blocking off the airway.
"OB is the major obstacle to prolonged survival following lung transplantation. Survival following lung transplantation is significantly poorer as compared to transplantation of other organs" (www.virtualmedicalcentre.com). Between 50 to 80 percent of patients have been diagnosed with this OB within five years of transplantation.
Risk factors include those patients who experience multiple or severe episodes of rejections especially shortly following transplantation, mismatched HLA (the component of the human body that determines transplant compatibility), pneumonia caused by the cytomegalovirus, or who have sustained injury to the airways or transplanted tissue.
This condition is progressive and will end in death, although the actual progression of the disease will vary from patient to patient. "The death rate at 3 years after the start of obliterative bronchiolitis is more than 50%. The survival rate at 5 years after the start of the disease is only 30 to 50%. Patients who develop obliterative bronchiolitis within the first three years after transplantation have a poorer outcome. A majority of these patients have a greater decline in lung function, greater need for oxygen and a higher rate of transplant failure (requiring transplantation) or death" (www.virtualmedicalcentre.com).
Treatment usually consists of oxygen supplementation, bronchodilators, immunosuppressants, and second transplants.
Sources: www.epler.com; http://emedicine.medscape.com; www.medscape.com; http://path.upmc.edu; www.virtualmedicalcentre.com; http://medical-dictionary.thefreedictionary.com